JP7260747B2 - Cutting inserts, indexable ball end mills - Google Patents

Description

The present invention provides a cutting insert that is detachably attached to an insert mounting seat formed at the tip of an end mill body of an indexable ball end mill that rotates about its axis, and such a cutting insert is attached to the insert mounting seat of the end mill body. The present invention relates to a detachably mounted indexable ball end mill and an end mill body of such an indexable ball end mill.

As cutting inserts to be attached to such indexable ball end mills, for example, Patent Documents 1 and 2 disclose a rake face facing in the direction of rotation of the end mill body and an insert mounting seat facing the opposite side to the rake face. A seating surface to be seated on the bottom surface and a flank extending around the rake surface and the seating surface are provided. Two cutting edges each provided with an arcuate cutting edge portion extending in an arc when viewed and a linear cutting edge portion extending in contact with the arcuate cutting edge portion are divided into an arcuate cutting edge portion and a linear cutting edge. It is described that the portions are alternately positioned in the circumferential direction of the rake face.

Here, in these Patent Documents 1 and 2, in order to reduce the cutting resistance and to divide the chips, the rake face is formed with a concave groove-like nick that reaches the cutting edge and opens to the flank face. things are also listed. Further, in Patent Document 3, a major cutting edge and a minor cutting edge are provided facing each other on the ridgeline of the upper surface facing the seating surface, and the major cutting edge and the minor cutting edge are asymmetrical. The arc-shaped cutting edge is longer than the arc-shaped cutting edge of the minor cutting edge and performs the main cutting. A cutting insert for a curved indexable ball end mill and an indexable ball end mill are described.

Japanese Patent No. 4771547 U.S. Pat. No. 7,309,193 JP-A-11-197933

By the way, like the cutting insert described in Patent Document 3, the cutting edge has an asymmetrical major cutting edge and minor cutting edge, and the arcuate cutting edge portion of the major cutting edge is the arcuate cutting edge of the minor cutting edge. Patent Documents 1 and 2 describe cutting inserts in which the main cutting edge and the minor cutting edge are formed in a convex curved shape that protrudes in a direction away from the seating surface in a side view. When a nick is formed on the rake face as described above, if this nick overlaps with the most convex point from the seating surface of the convex curvilinear cutting edge as described above, the cutting edge will be at the end of the nick will be cut into the work material from the

Therefore, if a large cutting load acts on the cutting edge in the vicinity of the nick during cutting, stress is concentrated on the edge of the nick, which may cause damage such as chipping to the cutting insert. In particular, like the cutting insert described in Patent Document 3, the circumferential length of the arcuate cutting edge portion of the major cutting edge is longer than the circumferential length of the arcuate cutting edge portion of the minor cutting edge, When the arc-shaped cutting edge portion of the main cutting edge is intended to perform the main cutting, the nick formed on the rake face of the arc-shaped cutting edge portion of the main cutting edge If it overlaps with the most convex point of the main cutting edge that is the most convex with respect to the seating surface of the part, a large impact cutting load will act on the end of this overlapped nick when it bites into the work material. , the risk of damage to the cutting insert from the end of this nick is even greater.

The present invention has been made under such a background, and in particular, a cutting insert for an indexable ball end mill having a basic shape in which the main cutting edge is formed in a convex curved shape that is convex in the rotational direction of the end mill, When a concave groove-shaped nick that reaches the main cutting edge and opens to the flank face is formed on the rake face, even if a large cutting load acts on the main cutting edge near this nick, the edge of the nick will not reach the cutting insert. In addition to providing a cutting insert capable of preventing chipping, etc., an indexable ball end mill to which such a cutting insert is detachably attached, and an end mill body of such an indexable ball end mill intended to provide.

In order to solve the above-mentioned problems and achieve these objects, the cutting insert of the present invention is attached to and detached from an insert mounting seat formed at the tip of the end mill body of an indexable ball end mill that rotates about its axis. A removably mounted cutting insert, comprising: a rake face oriented in the direction of rotation of the end mill body; a seating face opposite to the rake face and seated on the bottom surface of the insert mounting seat; and a flank extending around the seating surface, and an arc-shaped cutting edge extending in an arc shape in a plan view viewed from the direction facing the rake surface at the intersection ridgeline between the rake surface and the flank surface. and a linear cutting edge portion extending in contact with the arcuate cutting edge portion. One of the two cutting edges is a major cutting edge and the other is a minor cutting edge. The rake face of the main cutting edge has a concave groove that reaches the main cutting edge and opens to the flank face. is formed, and at least in the main cutting edge, the arc-shaped cutting edge portion moves away from the seating surface side as it separates from the linear cutting edge portion except for the nick, and then moves away from the seating surface side. The nick is the most convex of the main cutting edge where the arc-shaped cutting edge portion in the basic shape of the main cutting edge is the most convex with respect to the seating surface. The main cutting edge is arranged at a position different from the point, and in the above main cutting edge, the major cutting edge around the rotation axis passing through the center of the arc-shaped cutting edge portion in the plan view and parallel to the linear cutting edge portion In the cross section along the rotation axis of the rotation locus of, from the center of the arc-shaped cutting edge portion of the rotation axis to the end side opposite to the contact point of the arc-shaped cutting edge portion with the linear cutting edge portion and a straight line connecting the center and the most convex point of the main cutting edge intersect at an angle within the range of 43° to 47°.

Also, in the indexable ball end mill of the present invention, the cutting insert configured as described above is detachably attached to an insert mounting seat formed at the tip of the end mill body that rotates around the axis. Characterized by Further, the end mill main body of the present invention is an end mill main body that rotates about an axis, wherein a cutting insert configured as described above is detachably attached to an insert mounting seat formed at a tip portion, and the insert The bottom surface of the mounting seat is characterized by projecting a convex portion with which the wall surface of the groove portion abuts.

In the cutting insert and indexable ball end mill configured as described above, the arc-shaped cutting edge portion of the major cutting edge, which is longer in the circumferential direction than the arc-shaped cutting edge portion of the minor cutting edge, has the nick However, in this basic shape of the main cutting edge, the arc-shaped cutting edge is arranged at a position different from the most convex point of the main cutting edge with respect to the seating surface. It will not cut into the work material from the

For this reason, even if a large cutting load acts when the main cutting is performed by the main cutting edge, a large impact cutting load does not act on the edge of the nick when the main cutting edge bites, and the nick does not. It is possible to prevent the cutting insert from being damaged such as chipping from the end. Therefore, according to the cutting insert and the indexable ball end mill configured as described above, it is possible to perform stable cutting over a long period of time.

At least one nick of the main cutting edge is arranged on the end side opposite to the point of contact between the arc-shaped cutting edge portion and the linear cutting edge portion from the main cutting edge maximum convex point. It is desirable to be As a result, the chips generated by cutting into the work material from the arcuate cutting edge portion of the arc-shaped cutting edge portion of the main cutting edge can be divided before the chips are elongated or widened. Reduction in cutting resistance can be assured.

Further, in the main cutting edge, the rotational trajectory of the main cutting edge around the rotational axis that passes through the center of the arc-shaped cutting edge portion in plan view and is parallel to the linear cutting edge portion is along the rotational axis. In a cross section, a portion of the rotating shaft extending from the center of the arc-shaped cutting edge toward the end opposite to the point of contact with the linear cutting edge of the arc-shaped cutting edge, It is desirable that the straight line connecting the point of maximum convexity of the cutting edge intersects at an angle within the range of 43° to 47°.

If this angle is in the range of more than 47° or less than 43°, the most convex point of the major cutting edge is on the contact side of the arc-shaped cutting edge with the linear cutting edge, or on the contact point with this contact. If it is positioned too far on the opposite end side, the arc-shaped cutting edge of the main cutting edge will cut into the work material from the outer circumference of the rear end or the inner circumference of the tip of the indexable ball nose end mill. There is a possibility that the cutting resistance cannot be sufficiently reduced.

On the other hand, the rake face of the minor cutting edge is also formed with a groove-shaped nick that reaches the minor cutting edge and opens onto the flank face. Except for the above, if the secondary cutting edge has a basic shape formed in a convex curve that moves away from the seating surface side and then approaches the seating surface side as it moves away from the linear cutting edge portion, The nick of the cutting edge is such that the most recessed position toward the seating surface in the opening to the flank is the sub cutting edge where the arc-shaped cutting edge in the basic shape of the sub cutting edge is the most convex with respect to the seating surface. It is desirable that it be arranged at a position different from the point of maximum convexity of the cutting edge.

Since the cutting load acting on the arc-shaped cutting edge portion of the minor cutting edge is smaller than that of the major cutting edge, the minor cutting edge The most recessed position of the nick on the seating surface side should not coincide with the most convex point of the minor cutting edge where the arc-shaped cutting edge of the minor cutting edge is most convex with respect to the seating surface. Thus, it is possible to prevent the cutting insert from being damaged such as chipping from the edge of the nick of the minor cutting edge. However, it is of course more desirable for the minor cutting edge to dispose the entire nick at a position different from the most convex point of the minor cutting edge, as in the case of the major cutting edge.

It should be noted that such a nick of the minor cutting edge is such that the most recessed position toward the seating surface in the opening to the flank face is opposite to the nick of the arcuate cutting edge portion of the major cutting edge. It is desirable that the contact point between the arcuate cutting edge portion and the linear cutting edge portion of the minor cutting edge be located on the contact side of the blade's most convex point. That is, since the arc-shaped cutting edge portion of the minor cutting edge is shorter in the circumferential direction than the arc-shaped cutting edge portion of the major cutting edge, the position of the minor cutting edge that is most recessed toward the seating surface side of the nick is the minor cutting edge. By arranging it on the contact side of the arc-shaped cutting edge portion and the linear cutting edge portion of the blade, it is possible to divide the chips generated by the arc-shaped cutting edge portion of the minor cutting edge into substantially equal widths.

Furthermore, in the minor cutting edge, the rotational locus of the minor cutting edge around the rotational axis that passes through the center of the arc-shaped cutting edge portion in plan view and is parallel to the linear cutting edge portion along the rotational axis In a cross section, a portion of the rotating shaft extending from the center of the arc-shaped cutting edge toward the end opposite to the point of contact with the linear cutting edge of the arc-shaped cutting edge, the center and the secondary It is desirable that the straight line connecting the point of maximum convexity of the cutting edge intersects at an angle within the range of 43° to 47°.

Similar to the major cutting edge convexity point of the arc-shaped cutting edge portion of the major cutting edge, when this angle is in the range exceeding 47° or in the range below 43°, the minor cutting edge convexity point The arc-shaped cutting edge is positioned too far on the side of the contact with the linear cutting edge, or on the end opposite to this contact, and the arc-shaped cutting edge of the minor cutting edge is positioned behind the indexable ball end mill. Since the workpiece is cut from the outer peripheral side of the end or the inner peripheral side of the tip, there is a possibility that the cutting resistance cannot be sufficiently reduced.

As described above, according to the present invention, it is possible to prevent the arc-shaped cutting edge portion of the main cutting edge from cutting into the work material from the end of the nick. When biting into the work material, a large impact cutting load acts on the edge of the nick, which can prevent damage such as chipping of the cutting insert. can be done.

It is a perspective view showing one embodiment of the cutting insert of the present invention. FIG. 2 is a plan view of the embodiment shown in FIG. 1 viewed from a direction facing the rake face; FIG. 2 is a bottom view of the embodiment shown in FIG. 1 viewed from a direction facing the seating surface; FIG. 3 is a side view seen in the direction of an arrow A in FIG. 2; FIG. 3 is a side view seen in the direction of an arrow B in FIG. 2; FIG. 3 is a side view seen in the direction of an arrow C in FIG. 2; FIG. 3 is a side view seen in the direction of an arrow D in FIG. 2; FIG. 3 is a side view seen in the direction of an arrow E in FIG. 2; FIG. 9 is a perspective view of the tip of an end mill body showing one embodiment of an indexable ball end mill and an end mill body of the present invention in which the cutting inserts of the embodiment shown in FIGS. 1 to 8 are attached to two insert mounting seats, respectively. Figure 10 is a front view of the embodiment shown in Figure 9; FIG. 11 is a bottom view of FIG. 10 viewed in the direction of arrow A; FIG. 11 is a side view seen in the direction of an arrow B in FIG. 10; FIG. 10 is a perspective view showing the positional relationship between two cutting inserts in the indexable ball end mill of the embodiment shown in FIG. 9; FIG. 14 is a perspective view of the two cutting inserts whose positional relationship is shown in FIG. 13 as viewed from a direction facing the rake face of the first cutting insert whose main cutting edge is used for cutting;

FIGS. 1 to 8 show one embodiment of the cutting insert of the present invention, and FIGS. 9 to 12 show two cutting inserts of this embodiment attached to an insert mounting seat. 13 and 14 show the positional relationship of two cutting inserts in the indexable ball end mill of this embodiment.

The cutting insert 1 of the present embodiment is made of a hard material such as cemented carbide and is formed into a leaf-like plate shape in plan view as shown in FIG. 2 . The upper surface of this cutting insert 1 is the leaf-shaped rake face 2 as described above. The lower surface facing away from the rake surface 2 is a leaf-shaped flat seating surface 3 that is substantially similar to the rake surface 2 and is seated on the bottom surface of the insert mounting seat. A flank 4 is a side surface extending circumferentially between and the seating surface 3 .

At the intersection ridgeline between the rake face 2 and the flank face 4, arcuate cutting edge portions 5a and 6a extending arcuately as shown in FIG. Two cutting edges each having linear cutting edge portions 5b and 6b extending in contact with the arcuate cutting edge portions 5a and 6a are connected to the arcuate cutting edge portions 5a and 6a and the linear cutting edge portions 5b and 6b. They are formed alternately in the circumferential direction of the rake face 2 . One of these two cutting edges, a first cutting edge, is a major cutting edge 5 and the other second cutting edge is a minor cutting edge 6 .

Further, the flank 4 is inclined toward the inner peripheral side of the cutting insert 1 as it goes from the rake face 2 to the seating surface 3 side, and the cutting insert 1 of this embodiment is a positive type cutting insert. there is Further, a mounting hole 7 having a circular cross section formed so as to pass through the cutting insert 1 is opened at the center of the rake face 2 and the seating face 3 . The inner diameter of the side portion is formed so as to decrease toward the seating surface 3 side.

Here, in the plan view facing the rake face 2, the arc-shaped cutting edge portion 5a of the main cutting edge 5 has a substantially 1/4 arc shape. On the other hand, the arc-shaped cutting edge portion 6a of the minor cutting edge 6 has the same radius as the arc-shaped cutting edge portion 5a of the major cutting edge 5, but the length in the circumferential direction of the arc-shaped cutting edge portion of the major cutting edge 5. It is shorter than 5a, that is, it is formed in the shape of an arc shorter than a quarter arc. Along with this, the linear cutting edge portion 5b of the major cutting edge 5 is made shorter than the linear cutting edge portion 6b of the minor cutting edge 6. As shown in FIG. That is, the cutting insert 1 of this embodiment is not symmetrical about the center line of the mounting hole 7 by 180 degrees, but asymmetrical.

The linear cutting edge portions 5b and 6b of the major cutting edge 5 and the minor cutting edge 6 are the same as the arcuate cutting edge portion 5a of the major cutting edge 5 and the linear cutting edge portion 6b of the minor cutting edge 6 in the above-described plan view. from the first end 2a of the rake face 2 where the two intersect to the second end of the rake face 2 where the linear cutting edge 5b of the major cutting edge 5 and the arcuate cutting edge 6a of the minor cutting edge 6 intersect They extend closer to each other toward the portion 2b. These first and second end portions 2a and 2b are chamfered so as to intersect the arcuate cutting edge portions 5a and 6a and the linear cutting edge portions 5b and 6b of the major cutting edge 5 and the minor cutting edge 6 at an obtuse angle. formed in the shape of The first end 2a is positioned closer to the seating surface 3 than the second end 2b.

Further, the arcuate cutting edge portions 5a and 6a of the major cutting edge 5 and the minor cutting edge 6 are separated from the seating surface 3 as they are separated from the respective linear cutting edge portions 5b and 6b, except for nicks which will be described later. It is formed to have a basic shape of a convex curve that approaches the seating surface 3 side after cutting, and the convex curve formed by these arc-shaped cutting edge portions 5a and 6a becomes convex farthest from the seating surface 3. The point (the most protruding point from the seating surface 3) is the major cutting edge most convex point S5 and the minor cutting edge most convex point S6. The linear cutting edge portions 5b and 6b of the major cutting edge 5 and the minor cutting edge 6 also have arcuate cutting edge portions as shown in FIGS. It is in contact with the convex curve formed by the portions 5a and 6a and extends in a substantially straight line approaching the seating surface 3 side as the distance from the arcuate cutting edge portions 5a and 6a increases.

Here, in the main cutting edge 5, a rotation axis passing through the center P of the arcuate cutting edge portion 5a in plan view and parallel to the linear cutting edge portion 5b (an axis O of the end mill main body 11 to be described later) is rotated. In the cross section along the rotation axis of the rotation locus of the main cutting edge 5, as shown on the right side of FIG. A portion extending toward the end opposite to the contact point Q5 with the cutting edge portion 5b (the first end 2a side; in the case of an indexable ball end mill, the tip end side of the end mill body 11, which will be described later); A straight line L5 connecting the cutting edge maximum convex point S5 intersects at an angle θ5 within the range of 43° to 47°. In this embodiment, this angle θ5 is set to 45°.

14 (however, the left side of FIG. 4 is a bottom view of the minor cutting edge 6 as seen from the seating surface 3 side). Passing through the center P of the arcuate cutting edge portion 6a that coincides with the center P of the arcuate cutting edge portion 5a, and parallel to the linear cutting edge portion 6b (similarly, the axis O of the end mill body 11 described later) around In a cross-section along the rotation axis of the rotation locus of the minor cutting edge 6, a point of contact Q6 between the center P of the arcuate cutting edge portion 6a and the linear cutting edge portion 6b of the arcuate cutting edge portion 6a of the rotation axis. is a portion extending to the opposite end side (second end portion 2b side; similarly, in the case of an indexable ball end mill, the tip end side of the end mill body 11, which will be described later); intersects at an angle θ6 within the range of 43° to 47°. In this embodiment, this angle θ6 is also set to 45°.

Further, around the opening of the mounting hole 7 in the central portion of the rake face 2, there is a substantially elliptical shape in plan view that protrudes in a direction away from the seating surface 3 more than the major cutting edge 5 and the minor cutting edge 6. A protrusion 2c is formed. The upper end surface of this protrusion 2c is a flat surface parallel to the seating surface 3, and the mounting hole 7 opens to the upper end surface of this protrusion 2c. Furthermore, the outer peripheral surface of the protrusion 2c is inclined toward the inner side of the rake face 2 toward the upper end surface. Further, the rake face 2 extends toward the seating surface 3 as it moves away from the major cutting edge 5 and the minor cutting edge 6 and extends toward the inner side of the rake face 2, and then forms a concave curved surface on the outer peripheral surface of the protrusion 2c. are connected.

Furthermore, the flanks 4 connected to the linear cutting edge portions 5b and 6b of the major cutting edge 5 and the minor cutting edge 6 are formed in an inclined flat shape as described above. On the rake face 2 side, the flank 4 connected to the arcuate cutting edge portions 5a and 6a of the major cutting edge 5 and the minor cutting edge 6 extends in the circumferential direction of the cutting insert 1 along these arcuate cutting edge portions 5a and 6a. However, on the seating surface 3 side of the flank 4 of the arcuate cutting edge portion 5a of the main cutting edge 5, there is a flat portion 4a inclined flat as shown in FIGS. is formed.

A groove portion 8 is formed in the seating surface 3 . Here, in this embodiment, as shown in FIG. 7 and are formed on opposite sides of each other with the opening therebetween. The first groove 8A is formed closer to the first end 2a of the rake face 2 than the opening of the mounting hole 7, and the second groove 8B is formed closer to the second end 2b of the rake face 2. there is

These grooves 8 are formed in a substantially rectangular cross-section perpendicular to the direction in which the grooves 8 extend and are flattened in the direction in which the mounting holes 7 extend. and a bottom surface 8c parallel to the seating surface 3 extending between the first and second wall surfaces 8a and 8b. The first wall surface 8a of each groove 8 faces the first end 2a of the rake face 2, and the second wall surface 8b faces the second end 2b of the rake face 2. As shown in FIG. The intersection ridges between the first and second wall surfaces 8a and 8b and the seating surface 3 are chamfered with convex curved surfaces, and the corners where the first and second wall surfaces 8a and 8b and the bottom surface 8c intersect are concave. It is formed in a curved shape.

The first groove portion 8A opens on the flank surface 4 that continues to the linear cutting edge portion 6b of the minor cutting edge 6, and opens on the flank surface 4 that continues to the arcuate cutting edge portion 5a of the major cutting edge 5. It is formed in the shape of a blind groove that does not The end portion of the first groove portion 8A on the side of the arc-shaped cutting edge portion 5a of the main cutting edge 5 continues from the bottom surface 8c to the seating surface 3 so as to form a concave surface. Furthermore, in the first groove portion 8A, the first and second wall surfaces 8a and 8b extend parallel to each other in the bottom view. The end portion of the groove portion 8A on the side of the arcuate cutting edge portion 5a of the main cutting edge 5 extends perpendicular to the first and second wall surfaces 8a and 8b. is formed in a substantially trapezoidal shape when viewed from the direction facing the .

On the other hand, in this embodiment, the second groove portion 8B is formed on both the flank 4 that continues to the linear cutting edge portion 5b of the major cutting edge 5 and the flank surface 4 that continues to the arcuate cutting edge portion 6a of the minor cutting edge 6. It is formed in the shape of an open through groove. In this embodiment, the second groove portion 8B has a narrow portion 9 in which the groove width narrows from one end side to the other end side in the direction in which the second groove portion 8B extends. Here, in the present embodiment, the side of the flank 4 connected to the linear cutting edge portion 5b of the major cutting edge 5 is one end side of the second groove portion 8B, and the arcuate cutting edge portion 6a of the minor cutting edge 6 The continuous flank 4 side is the other end side.

Further, as shown in FIG. 3, the entire second groove portion 8B is the narrow portion 9 in this embodiment. In the present embodiment, the width of the narrow portion 9 is made constant from one end side to the other end side of the second groove portion 8B. That is, the first and second wall surfaces 8a and 8b of the second groove portion 8B are formed so as to approach each other linearly from one end side to the other end side in the bottom view.

Furthermore, the opening of the second groove portion 8B to the flank 4 connected to the arcuate cutting edge portion 6a of the minor cutting edge 6 is located at a higher angle than the minor cutting edge peak point S6. It is located on the part 6b side. Specifically, in the bottom view, the straight line L6 connecting the minor cutting edge most convex point S6 and the center P of the arc formed by the arcuate cutting edge portion 6a of the minor cutting edge 6 and the straight line of the minor cutting edge 6 The end of the intersection ridge (excluding the chamfered portion) between the first wall surface 8a of the second groove portion 8B and the flank surface 4 facing the side of the cutting edge portion 6b and the center P is connected to the seating surface 3 side. A first crossing angle with a straight line (not shown) is in the range of 5° to 60°.

The groove width W1 (not shown) at the other end of the narrow portion 9 (the other end of the second groove portion 8B in this embodiment) is the width of the groove portion (second groove portion 8B) having the narrow portion 9. 0.05×r to 0.18 with respect to the radius r (not shown) of the arc-shaped cutting edge portion (arc-shaped cutting edge portion 6a of the minor cutting edge 6) located on the other end side as viewed from the seating surface 3 side xr, for example, 1 mm to 7 mm. However, if the shape of the circular arc-shaped cutting edge 6a viewed from the seating surface 3 side is deviated from the circular arc, a virtual arc that is closest to the deviated shape is drawn, and this virtual , the radius r will be obtained from the arc of .

On the other hand, the groove width W2 (not shown) at one end of the narrow portion 9 satisfies W2>W1, and the groove portion (second groove portion 8B) having the narrow width portion 9 has an arc-shaped cutting portion located on the other end side. 0.10×r to 0.10×r to 0.10×r to 0.10×r to 0.10×r to 0.10×r to a radius r of the blade portion (arc-shaped cutting edge portion 6a of the minor cutting edge 6) in a bottom view viewed from the seating surface 3 side or a plan view viewed from the rake face 2 side. In the range of 30×r, the length R (not shown) of the linear cutting edge portion 5b of the main cutting edge 5 in the above plan view or bottom view is in the range of 0.10×R to 0.32×R. It is said that

Note that when the first and second wall surfaces 8a and 8b extend linearly in a bottom view viewed from the direction facing the seating surface 3, the groove widths W1 and W2 are equal to those of the first and second wall surfaces 8a and 8b. is the width in the direction perpendicular to the bisector of the straight line formed by the wall surfaces 8a and 8b, one groove wall surface (for example, the first wall surface 8a) is curved, When the wall surface 8b) of 2 is linear, it is the width in the direction perpendicular to the linear groove wall surface.

In such a cutting insert 1, the rake face 2 of the main cutting edge 5 is formed with a groove-like nick 10 that reaches the main cutting edge 5 and opens to the flank face 4. The nick 10 of No. 5 is arranged at a position different from the major cutting edge convexity point S5. In this embodiment, the rake face 2 of the minor cutting edge 6 is also formed with a groove-shaped nick 10 that reaches the minor cutting edge 6 and opens to the flank face 4 . 10 is also arranged at a position different from the minor cutting edge convexity point S6.

In this embodiment, the nick 10 is formed in the shape of a concave groove by notching the rake face 2 in the shape of a concave curve such as a concave arc when viewed from the direction facing the flank face 4 . The distance between and is gradually increased toward the inner side of the rake face 2, and is formed so as to rise from the rake face 2 before reaching the upper end surface of the protrusion 2c. A valley bottom line passing through the most recessed position M on the seating surface 3 side of the opening of the nick 10 to the flank surface 4 and connecting the portion where the distance from the seating surface 3 is small toward the inside of the rake surface 2 is It extends so as to be substantially perpendicular to the cutting edge in plan view facing the rake face 2 . The boundary between the nick 10 and the rake face 2 is rounded to form a convex surface along the opening to the flank face 4 .

Further, in this embodiment, a plurality of (two) nicks 10 are formed at intervals on each cutting edge (major cutting edge 5 and minor cutting edge 6). Of these, the two nicks 10 of the major cutting edge 5 are both formed to reach the arcuate cutting edge portion 5a, and one of the nicks 10 of the minor cutting edge 6 reaches the arcuate cutting edge portion 6a. In addition, the remaining one is formed so as to reach the linear cutting edge portion 6b.

These nicks 10 align the two cutting inserts 1 so that the centers P of the arcuate cutting edge portions 5a and 6a of the major cutting edge 5 and the minor cutting edge 6 are aligned with each other, and these arcuate cutting edge portions 5a and 6a are aligned. When 6a and linear cutting edge portions 5b, 6b are superimposed and viewed, a nick 10 reaching the main cutting edge 5 of one of the overlapping cutting inserts 1 and a nick reaching the minor cutting edge 6 of the other cutting insert 1 10 are formed so as to overlap the cutting edge extending between the nicks 10 without overlapping each other.

Furthermore, the nicks 10 of the major cutting edge 5 and minor cutting edge 6 are shown in FIG. , the opening of the groove 8 to the flank 4 is located at a position different from that of the opening. In this embodiment, not only the position M that is most recessed toward the seating surface 3 side, but the entire opening to the flank surface 4 is the groove portion 8 as shown in FIG. It is formed so as not to overlap the opening to the flank 4 . However, the nick 10 reaching the minor cutting edge 6 is slightly different from the opening of the groove 8 to the flank 4 in a perspective view from the rake face 2 side, the edge part away from the most recessed position M on the seating surface 3 side. They may overlap each other.

Furthermore, in this embodiment, in the main cutting edge 5, in a perspective view from the rake face 2 side, the position M of the nick 10 that is most recessed toward the seating face 3 in the opening to the flank face 4 is the groove portion. 8 on the side of the first end portion 2a opposite to the contact point Q5 with the linear cutting edge portion 5b in the arcuate cutting edge portion 5a. In particular, in the present embodiment, as described above, in the main cutting edge 5, the groove portion 8 (second groove portion 8B) opens only in the flank 4 of the linear cutting edge portion 5b as described above. , and two nicks 10 are formed on the rake face 2 of the arcuate cutting edge portion 5a.

Further, in the present embodiment, at least one nick 10 of the main cutting edge 5 is located in a direction opposite to the point of contact Q5 between the arcuate cutting edge portion 5a and the linear cutting edge portion 5b rather than the main cutting edge maximum convexity point S5. It is arranged on the first end 2a side. Specifically, the two nicks 10 formed to reach the main cutting edge 5 in this embodiment are located on the contact point Q5 side and the first end portion 2a side with the main cutting edge most convex point S5 therebetween. are placed.

Furthermore, in the present embodiment, the position M of the two nicks 10 of the minor cutting edge 6, which is the most recessed toward the seating surface 3 in the opening to the flank surface 4, is located further than the minor cutting edge peak point S6. It is arranged on the contact point Q6 side between the arcuate cutting edge portion 6a and the linear cutting edge portion 6b of the blade 6. As shown in FIG. In addition, the grooves 8 (first and second grooves 8A and 8B) that open to the flank 4 of the minor cutting edge 6 are located closer to the arcuate cutting edge 6a of the minor cutting edge 6 than the minor cutting edge peak point S6. and the linear cutting edge portion 6b.

Furthermore, at least one nick 10 of the minor cutting edge 6 is positioned such that the most recessed position M toward the seating surface 3 in the opening to the flank surface 4 is the most convex point S6 of the minor cutting edge and the relief of the minor cutting edge 6. It is arranged between the groove portion 8 that opens to the surface 4 . Here, in the present embodiment, one nick 10 of the two nicks 10 of the minor cutting edge 6 is the minor cutting edge most convex point S6 and the opening to the flank surface 4 of the minor cutting edge 6 of the second groove portion 8B. Another nick 10 is located on the linear cutting edge portion 6b beyond the contact point Q6, and is located between the minor cutting edge peak point S6 and the minor cutting edge 6 of the first groove portion 8A. and the opening to the flank 4.

Here, the cutting insert 1 made of hard material such as cemented carbide is manufactured according to the basic steps of powder metallurgy. That is, when the cutting insert 1 is made of a cemented carbide, granulated granulated powder containing tungsten carbide powder and cobalt powder as main components and, if necessary, chromium, tantalum, etc. as subcomponents is used to mold the mold. Perform powder press molding using

The press-formed body thus obtained is sintered for a predetermined time in a sintering furnace controlled to an appropriate atmosphere and temperature, whereby a sintered body that becomes the cutting insert 1 can be manufactured. The basic shape of the cutting insert 1 is reflected by the design of the die, and the detailed shape of the cutting insert 1 is obtained by die molding. Furthermore, in order to improve the precision of the cutting edge shape of the cutting insert 1, grinding processing using a grinding wheel may be performed as necessary.

The cutting insert 1 constructed in this way is detachably attached to the insert mounting seat 12 formed at the tip of the end mill body 11 as shown in FIGS. constitute an embodiment. The end mill main body 11 is formed of a metal material such as steel, and the tip portion thereof has a cylindrical shape centered on the axis O on the base end side, and a base end side cylinder centered on the axis O on the tip end side. It has a convex hemispherical shape with a radius equal to . The indexable ball end mill of this embodiment is attached to the insert mounting seat 12 by rotating the end mill main body 11 about the axis O in the end mill rotation direction T and sending it out in a direction intersecting the axis O. A cutting insert 1 is used to cut a material to be cut.

Here, in this embodiment, two tip pockets 13 are formed by notching the outer circumference of the end mill main body 11, and inserts are attached to the bottom faces of these tip pockets 13 facing the end mill rotation direction T, respectively. Seats 12 are circumferentially spaced and formed opposite each other. The first and second cutting inserts 1A and 1B of the same shape and size based on the above-described embodiment are attached to these two insert mounting seats 12, respectively.

These insert mounting seats 12 have a flat bottom surface 12a facing in the end mill rotation direction T, a tip inner peripheral wall surface 12b extending from the bottom surface 12a in the end mill rotation direction T and facing the outer peripheral side of the end mill main body 11, and a tip outer peripheral wall surface. and a wall surface 12c on the outer peripheral side of the rear end facing the . The wall surfaces 12b and 12c are formed in a planar shape that inclines outwardly of the insert mounting seat 12 as the distance from the bottom surface 12a increases. The flat flank 4 connecting to the linear cutting edge portions 5b and 6b of the minor cutting edge 6 and the flat portion 4a of the flank 4 connecting to the arcuate cutting edge portions 5a and 6a on the side of the seating surface 3 can be contacted. ing.

A concave portion 12d is formed between the wall surfaces 12b and 12c to avoid contact with the curved flank surface 4 of the cutting insert 1. As shown in FIG. Further, the bottom surface 12a is formed with a screw hole (not shown) into which a clamp screw 15 inserted through the mounting hole 7 of the cutting insert 1 is screwed. The center line of this threaded hole is a plane connected to the linear cutting edge portions 5b and 6b of the major cutting edge 5 and the minor cutting edge 6 with the seating surface 3 of the cutting insert 1 seated on the bottom surface 12a as described above. The center of the mounting hole 7 of the cutting insert 1 is in contact with the wall surfaces 12b and 12c with the planar portion 4a of the flank 4 on the side of the seating surface 3 connected to the curved flank 4 and the arcuate cutting edge portions 5a and 6a. It is slightly eccentric to the concave portion 12d side of the line.

Of these two insert mounting seats 12, the first insert mounting seat 12A is formed by notching the tip of the end mill body 11 to a range including the axis O, as shown in FIGS. ing. In the first insert mounting seat 12A, the first cutting insert 1A is positioned on a convex hemisphere having the arc-shaped cutting edge portion 5a of the main cutting edge 5 extending from the vicinity of the axis O and having the center on the axis O. In addition, the linear cutting edge portion 5b of the main cutting edge 5 is attached so as to be positioned on a cylindrical surface centered on the axis O in contact with the convex hemisphere.

Therefore, the planar flank 4 continuous with the linear cutting edge portion 6b of the minor cutting edge 6 of the first cutting insert 1A is brought into contact with the wall surface 12b of the first insert mounting seat 12A, and the wall surface 12c is in contact with the wall surface 12c. The flat portion 4a of the flank 4 of the arc-shaped cutting edge portion 6a of the minor cutting edge 6 of the first cutting insert 1A is brought into contact.

On the bottom surface 12a of the first insert mounting seat 12A, a first convex portion 14A that can abut against the wall surface of the groove portion 8 formed in the seating surface 3 of the first cutting insert 1A is formed. and the wall surface 12c, and extends from the outer peripheral surface of the tip of the end mill body 11 toward the recess 12d to the front of the recess 12d with a space therebetween. Therefore, the second groove portion 8B of the groove portions 8 formed in the seating surface 3 of the first cutting insert 1A abuts against the first convex portion 14A, and the first insert mounting seat 12A contacts the first convex portion 14A. A convex portion with which the first groove portion 8A abuts is not formed.

Here, the first convex portion 14A has a substantially rectangular cross-section perpendicular to the direction in which the first convex portion 14A extends and is flattened in the end mill rotation direction T, and the entirety is a narrow portion 9. With respect to the second groove portion 8B, the overall width is increased from the other end side to the one end side (from the inner peripheral side to the outer peripheral side of the end mill body 11) in the direction in which the second groove portion 8B extends. is formed in

However, the width of the first protrusion 14A (the width in the direction perpendicular to the direction in which the first protrusion 14A extends) is (the width in the direction orthogonal to the extending direction of the second groove portion 8B), and the protrusion height from the bottom surface 12a of the first protrusion 14A is also the seating of the first cutting insert 1A. It is made slightly smaller than the depth of the second groove portion 8B from the surface 3.

On the other hand, the tip of the second insert mounting seat 12B of the two insert mounting seats 12 is slightly away from the axis O on the distal end side of the end mill main body 11, as shown in FIGS. made up of positions. The second cutting insert 1B is mounted on the second insert mounting seat 12B so that the arcuate cutting edge portion 6a of the minor cutting edge 6 of the second cutting insert 1B is mounted on the main cutting edge 5 of the first cutting insert 1A from a position away from the axis O. The linear cutting edge portion 6b of the minor cutting edge 6 is aligned with the linear cutting edge portion 5b of the major cutting edge 5 of the first cutting insert 1A. It is attached so as to be positioned on the above-mentioned cylindrical surface.

Therefore, the planar flank 4 continuous with the linear cutting edge portion 5b of the main cutting edge 5 of the second cutting insert 1B is brought into contact with the wall surface 12b of the second insert mounting seat 12B, and the wall surface 12c is in contact with the wall surface 12c. The flat portion 4a of the flank 4 of the arcuate cutting edge portion 5a of the main cutting edge 5 of the second cutting insert 1B is brought into contact.

A second convex portion 14B is formed on the bottom surface 12a of the second insert mounting seat 12B on the tip side of the screw hole, and a third convex portion 14B is formed between the screw hole and the wall surface 12c. A portion 14C is formed. These second and third protrusions 14B and 14C also extend from the outer peripheral surface of the tip of the end mill body 11 toward the inner peripheral side, and the second protrusion 14B extends toward the wall surface 12b of the second insert mounting seat 12B. The third protrusion 14C is formed to the front of the recess 12d of the second insert mounting seat 12B with a space to the wall 12b. Therefore, the second groove 8B of the second cutting insert 1B contacts the second projection 14B, and the first groove 8A of the second cutting insert 1B contacts the third projection 14C.

Further, the second and third protrusions 14B and 14C also have a substantially rectangular cross-section perpendicular to the direction in which the second and third protrusions 14B and 14C extend, which is flattened in the end mill rotation direction T, Of these, the second convex portion 14B is formed in the direction in which the second groove portion 8B extends, whereas the entire second groove portion 8B of the second cutting insert 1B that abuts thereon is the narrow portion 9. It is formed so that it becomes wider as a whole as it goes from the other end side to the one end side (from the outer peripheral side to the inner peripheral side of the end mill main body 11). The width of the third protrusion 14C is constant along the direction in which the third protrusion 14C extends.

Furthermore, the widths of the second and third protrusions 14B and 14C (the widths in the direction orthogonal to the direction in which the second and third protrusions 14B and 14C extend) are also the same as the second and first grooves 8B and 8A. is slightly smaller than the width at the position contacting the second and third protrusions 14B and 14C in the extending direction (the width in the direction perpendicular to the extending direction of the second and first grooves 8B and 8A). ing. Also, the protrusion heights of the second and third projections 14B and 14C from the bottom surface 12a of the second insert mounting seat 12B are also the same as the second and first groove portions 8B from the seating surface 3 of the second cutting insert 1B. It is slightly smaller than the depth of 8A.

The first and second cutting inserts 1A and 1B are seated on the first and second insert mounting seats 12A and 12B as described above, and a clamp screw 15 having an inverted truncated conical head is provided. is inserted into the mounting hole 7 and screwed into the screw hole. 1 is pressed against the side of the recess 12d.

At this time, in the first insert mounting seat 12A, the plane of the flank 4 connecting to the linear cutting edge portion 6b of the minor cutting edge 6 of the first cutting insert 1A and the flank surface 4 connecting to the arcuate cutting edge portion 6a The portion 4a is pressed against the wall surfaces 12b and 12c, respectively. In addition, in the second insert mounting seat 12B, the flank 4 continuous with the linear cutting edge portion 5b of the main cutting edge 5 of the second cutting insert 1B is pressed against the wall surface 12b, thereby The flat portion 4a of the flank 4 that continues to the blade portion 5a is pressed against the wall surface 12c.

Along with this, the second groove portion 8B of the first cutting insert 1A abuts against the first convex portion 14A of the first insert mounting seat 12A from the tip end side of the end mill body 11 . Therefore, the second wall surface 8b of the second groove portion 8B of the first cutting insert 1A abuts against the side surface 14a of the end mill body 11 facing the distal end side of the first protrusion 14A, and the second groove portion A small gap is provided between the first wall surface 8a and the first protrusion 14A at 8B.

Also, in the second insert mounting seat 12B, the second and first grooves 8B and 8A of the second cutting insert 1B are formed in the second and third projections 14B and 14C from the tip end side of the end mill body 11. abut. Therefore, the first wall surfaces 8a of the second and first grooves 8B and 8A abut on the side surfaces 14a of the end mill body 11 facing the tip side of the second and third protrusions 14B and 14C, respectively. 2. A slight gap is provided between the second wall surface 8b of the first grooves 8B and 8A and the second and third projections 14B and 14C. In this manner, the first and second grooves 8A and 8B abut against the first to third projections 14A to 14C, thereby preventing the cutting insert 1 from slipping due to load during cutting. .

In the indexable ball end mill configured as described above, the second cutting insert 1B has the arc-shaped cutting edge portion 6a of the minor cutting edge 6 and the major cutting edge 5 of the first cutting insert 1A as described above. The linear cutting edge portion 6b is positioned on the cylindrical surface where the linear cutting edge portion 5b of the main cutting edge 5 of the first cutting insert 1A is located. It can be installed in position.

These first and second cutting inserts 1A and 1B are arranged such that the centers P of the arcuate cutting edge portions 5a and 6a of the major cutting edge 5 and the minor cutting edge 6 are aligned with each other, and these arcuate cutting edges are When the portions 5a, 6a and the linear cutting edge portions 5b, 6b are superimposed and viewed, a nick 10 reaching the main cutting edge 5 of one of the overlapping cutting inserts 1 and the minor cutting edge 6 of the other cutting insert 1 are shown. The nicks 10 reaching the cutting edges 10 do not overlap each other, but overlap the cutting edge extending between the nicks 10 .

Therefore, by setting the feed amount per blade of the end mill body 11 to be smaller than the retraction amount of the nick 10 from the cutting edge in plan view facing the rake surface 2, the nick 10 is most recessed toward the seating surface 3 side. The position M is not cut into the work material, so that the chips can be divided and generated, and the cutting resistance can be reduced. On the machined surface of the work material, a ridge is left in the part left uncut by the nick 10, but this ridge is removed by the cutting edge of the cutting insert 1 on the opposite side when the end mill main body rotates 1/2. It is cut and removed by being cut.

In the cutting insert 1 and the indexable ball end mill configured as described above, the arc-shaped cutting edge portion 5a of the major cutting edge 5, which is longer than the arc-shaped cutting edge portion 6a of the minor cutting edge 6 in the circumferential direction, The reaching nick 10 is arranged at a position different from the main cutting edge most convex point S5 where the arcuate cutting edge portion 5a in the basic shape of the main cutting edge 5 is most convex with respect to the seating surface 3. Therefore, the main cutting edge cuts into the work material from this main cutting edge maximum convexity point S5, and does not cut into the work material from the end of the nick 10. FIG.

Therefore, when main cutting is performed by the main cutting edge 5 having a long arc-shaped cutting edge portion 5a in the circumferential direction, even if a large cutting load acts on the main cutting edge 5, the main cutting edge 5 is not affected by the cutting force. A large impact cutting load does not act on the end of the nick 10 when biting into the material to be cut, so damage such as chipping of the cutting insert 1 from the end of the nick 10 can be prevented. Therefore, according to the cutting insert 1 and the indexable ball end mill configured as described above, it is possible to perform stable cutting over a long period of time.

In this embodiment, at least one nick 10 of the major cutting edge 5 is formed at a position different from the major cutting edge convexity point S5. It is arranged on the side of the first end 2a opposite to the point of contact Q5 between the arcuate cutting edge 5a and the linear cutting edge 5b from the blade maximum convexity point S5. For this reason, the chips generated by cutting into the work material from the main cutting edge maximum convex point S5 of the arcuate cutting edge portion 5a of the main cutting edge 5 should be divided so as not to extend or widen. It is possible to achieve a reliable reduction in cutting resistance.

Furthermore, in the present embodiment, in the main cutting edge 5, along the rotation axis of the rotation locus around the rotation axis that passes through the center P of the arc-shaped cutting edge portion 5a in plan view and is parallel to the linear cutting edge portion 5b In a cross section, that is, a cross section along the axis O of the rotation trajectory of the main cutting edge 5 around the axis O of the end mill body 11, a straight line from the center P of the arcuate cutting edge 5a of the rotation shaft to the arcuate cutting edge 5a A portion extending toward the first end portion 2a opposite to the contact point Q5 with the shaped cutting edge portion 5b, that is, a portion extending from the center P of the axis O toward the tip end side of the end mill body 11, the center P and the main cutting edge maximum. A straight line L5 connecting the convex point S5 intersects at an angle θ5 within the range of 43° to 47°. Therefore, the main cutting edge 5 can cut into the work material from substantially the center of the arc-shaped cutting edge portion 5a, and the cutting resistance can be reliably reduced.

That is, when the angle θ5 is in the range of more than 47° or less than 43°, the point S5 of the main cutting edge is the point of contact Q5 between the arcuate cutting edge 5a and the linear cutting edge 5b. side, or the first end 2a side opposite to this contact Q5. Therefore, the arc-shaped cutting edge portion 5a of the main cutting edge 5 cuts into the work material from the outer circumference of the rear end or the inner circumference of the tip of the indexable ball end mill, thereby sufficiently reducing the cutting resistance. may not be possible.

On the other hand, in the present embodiment, the arc-shaped cutting edge portion 6a of the minor cutting edge 6, excluding the nick 10, also separates from the seating surface 3 side as it separates from the linear cutting edge portion 6b of the minor cutting edge 6, and then It has a basic shape formed in a convex curve that approaches the side. Therefore, like the arcuate cutting edge portion 5a of the major cutting edge 5, the arcuate cutting edge portion 6a of the minor cutting edge 6 is also the most convex minor cutting edge with respect to the seating surface 3 in this basic shape. Since the work material is cut from the point S6, the cutting resistance can be reduced.

In the present embodiment, a groove-shaped nick 10 is also formed on the rake face 2 of the minor cutting edge 6 to reach the minor cutting edge 6 and open to the flank face 4 . 10 is also formed at a position different from the minor cutting edge convexity point S6. Therefore, like the arcuate cutting edge portion 5a of the major cutting edge 5, the arcuate cutting edge portion 6a of the minor cutting edge 6 also cuts into the work material from the minor cutting edge's most convex point S6. Since impact cutting load does not act on the end of the nick 10 of the minor cutting edge 6 during cutting, damage to the cutting insert 1 from the end of the nick 10 of the minor cutting edge 6 can also be prevented. can.

However, the arcuate cutting edge portion 6a of the minor cutting edge 6 is shorter in the circumferential direction than the arcuate cutting edge portion 5a of the major cutting edge 5, and the cutting load acting thereon is smaller than that of the major cutting edge 5. Even if the entire nick 10 is not at a position different from the minor cutting edge maximum convex point S6 as in the embodiment, the position M of the minor cutting edge 6 where the nick 10 is most recessed toward the seating surface 3 is the minor cutting edge. If it is arranged at a position different from the most convex point S6, it is possible to prevent the cutting insert 1 from being damaged such as chipping from the end of the nick 10 of the minor cutting edge 6. FIG.

Further, in the present embodiment, the nick 10 of the minor cutting edge 6 is positioned so that the position M, which is the most recessed toward the seating surface 3 in the opening to the flank surface 4, is located more than the minor cutting edge peak point S6. is arranged on the contact point Q6 side between the arcuate cutting edge portion 6a and the linear cutting edge portion 6b. As described above, the arcuate cutting edge portion 6a of the minor cutting edge 6 is shorter in the circumferential direction than the arcuate cutting edge portion 5a of the major cutting edge 5, so that the nick 10 of the minor cutting edge 6 is seated. Position M, which is the most recessed on the surface 3 side, is on the contact point Q6 side between the arcuate cutting edge portion 6a of the minor cutting edge 6 and the linear cutting edge portion 6b, opposite to the arcuate cutting edge portion 5a of the major cutting edge. By arranging them, it becomes possible to divide the chips generated by the arc-shaped cutting edge portion 6a of the minor cutting edge 6 into pieces having substantially the same width.

Furthermore, in the present embodiment, the minor cutting edge 6 also rotates around the rotation axis passing through the center P of the arcuate cutting edge portion 6a of the minor cutting edge 6 in plan view and parallel to the linear cutting edge portion 6b. In a cross section along the rotation axis of the rotation locus of the blade 6, that is, in a cross section along the axis O of the rotation locus of the minor cutting edge 6 around the axis O of the end mill body 11, the circle of the minor cutting edge 6 of the rotation axis a portion extending from the center P of the arcuate cutting edge portion 6a to the end portion side opposite to the point of contact Q6 of the arcuate cutting edge portion 6a with the linear cutting edge portion 6b, i.e., the portion extending toward the tip end side of the end mill body 11; A straight line L6 connecting the center P and the minor cutting edge convexity point S6 intersects at an angle θ6 within the range of 43° to 47°. Therefore, the arc-shaped cutting edge portion 6a of the minor cutting edge 6 can be caused to cut into the work material from substantially the center thereof in the same manner as the major cutting edge 5, so that the cutting resistance can be reliably reduced.

That is, as in the case of the major cutting edge 5, when the angle θ6 exceeds 47° or falls below 43°, the minor cutting edge maximum convex point S6 is The arc-shaped cutting edge 6a of the minor cutting edge 6 is positioned too much on the side of the contact Q6 with the straight cutting edge 6b or on the side of the second end 2b opposite to this contact Q6, and the arc-shaped cutting edge 6a of the minor cutting edge 6 becomes an indexable ball. There is a possibility that cutting force cannot be sufficiently reduced because the workpiece is cut from the rear end outer circumference side or the tip inner circumference side of the end mill.

On the other hand, in the present embodiment, the most recessed position M toward the seating surface 3 in the opening of the nick 10 formed in the rake surface 2 to the flank surface 4 is shown in FIG. 2, the groove 8 formed in the seating surface 3 is arranged at a position different from the opening to the flank 4. As shown in FIG. That is, in the extending direction of the cutting edge, the recessed position M of the nick 10 on the seating surface 3 side does not overlap with the opening of the groove 8 to the flank surface 4 .

For this reason, between the most recessed position M of the nick 10 and the seating surface 3, the thickness of the cutting insert 1 can be secured to maintain the strength. Even if a large cutting load acts on the nick 10 and propagates from the most recessed position M of the nick 10 to the seating surface 3 side, the cutting insert 1 is prevented from being damaged such as chipping between the groove 8 and the groove 8. can be prevented. Therefore, according to the cutting insert 1 and the indexable ball end mill configured as described above, stable cutting can be performed over a long period of time even under cutting conditions where such a large cutting load acts.

In particular, in the present embodiment, these nicks 10 are formed not only at the most recessed position M on the seating surface 3 side, but also on the entire opening to the flank surface 4 in the perspective view from the rake surface 2 side. is formed so as not to overlap the opening to the flank 4 of the . Therefore, it is possible to prevent the cutting insert 1 from forming a thin portion due to even partial overlap of the nick 10 and the groove portion 8, thereby further reliably preventing the occurrence of damage such as chipping. be able to.

However, in the same manner as described above, especially in the minor cutting edge 6, the circumferential length of the arc-shaped cutting edge portion 6a is shorter than that of the major cutting edge 5, and the cutting load acting thereon is also small. If the position M that is most recessed to the side does not overlap with the groove portion 8, the edges and ends of the nick 10 that are farthest from the position M that is most recessed to the seating surface 3 side are seen from the rake face 2 side as described above. may slightly overlap with the opening of the groove 8 to the flank 4 at .

In addition, in the cutting insert of this embodiment, the second groove portion 8B of the groove portion 8 has a narrow portion 9 in which the groove width becomes narrower from one end side to the other end side in the direction in which the second groove portion 8B extends. have. As a result, the thickness of the cutting insert 1 can be ensured on the other end side where the groove width of the narrow portion 9 is narrowed, stress can be dispersed, and strength can be improved.

On the other hand, on the one end side of the narrow width portion 9, the width of the groove becomes wider. By forming the abutting portion so that the width increases from the other end side in the direction in which the second groove portion 8B extends toward the one end side, the mounting rigidity against the load during cutting is increased and the deviation of the cutting insert 1 is prevented. Movement can be reliably prevented.

Furthermore, in this embodiment, in the perspective view from the rake face 2 side of the main cutting edge 5, the position M of the nick 10 that is most recessed toward the seating face 3 in the opening to the flank face 4 is the second The first end 2a side opposite to the contact point Q5 with the linear cutting edge portion 5b in the arcuate cutting edge portion 5a than the opening of the groove portion 8B.

Therefore, the position M of the main cutting edge 5 that is most recessed toward the seating surface side of the nick 10 is closer to the arcuate cutting edge portion 5a side of the main cutting edge 5 than the opening of the second groove portion 8B. It will be arranged at a position different from the opening to the flank 4 of 8B. Therefore, even if the nicks 10 are formed in the arc-shaped cutting edge portion 5a of the major cutting edge 5, which is longer than the minor cutting edge 6 in the circumferential direction, the major cutting edge having the longer circumferential length can be formed. It is possible to reliably prevent damage to the cutting insert 1 due to a large cutting load acting on the arc-shaped cutting edge portion 5a of the 5.

In particular, in the case of this embodiment, in the main cutting edge 5, the second groove portion 8B is opened only in the flank surface 4 of the linear cutting edge portion 5b, and the arc-shaped cutting edge portion 8B A nick 10 is formed only on the rake face 2 of the blade portion 5a. Therefore, it is possible to reliably divide extended chips and wide chips generated by the arc-shaped cutting edge portion 5a of the major cutting edge 5, which is longer than the minor cutting edge 6 in the circumferential direction. Since the groove 8 does not open in the flank 4 of the arcuate cutting edge 5a of the major cutting edge 5, damage to the cutting insert 1 can be prevented more reliably.

Furthermore, in the present embodiment, the grooves 8 (the first and second grooves 8A and 8B) that open to the flank 4 of the minor cutting edge 6 are positioned further along the circle of the minor cutting edge 6 than the minor cutting edge peak point S6. It is open on the contact point Q6 side between the arcuate cutting edge portion 6a and the linear cutting edge portion 6b. Therefore, when the minor cutting edge 6 cuts into the work material from the minor cutting edge most convex point S6 as described above, the seating surface 3 on the side opposite to the minor cutting edge most convex portion S6 is The groove 8 that opens to the flank 4 of the blade 6 can prevent the bottom surface 12a of the second insert mounting seat 12B from becoming unsupported, and the arcuate cutting edge portion 6a of the minor cutting edge 6 can be prevented from being unsupported. It is possible to improve the support rigidity of the point S6.

Furthermore, in the present embodiment, at least one nick 10 of the minor cutting edge 6 has the most recessed position M toward the seating surface 3 in the opening to the flank surface 4 and the minor cutting edge most convex point S6. It is arranged between the groove portion 8 (second groove portion 8B) that opens to the flank surface 4 of the cutting edge 6 . As a result, chips generated by cutting into the work material from the minor cutting edge most convex point S6 can be immediately divided by the nick 10 between the groove portion 8 (second groove portion 8B) and the groove portion 8 By opening the second insert mounting seat 12B, the cutting load acting on the minor cutting edge 6 that is not supported by the bottom surface 12a of the second insert mounting seat 12B can be reduced.

1 (1A, 1B) cutting insert 2 rake face 3 seating surface 4 flank face 5 major cutting edge 5a arc-shaped cutting edge portion of major cutting edge 5 5b linear cutting edge portion of major cutting edge 5 6 minor cutting edge 6a minor cutting edge Circular cutting edge portion 6b of blade 6 Linear cutting edge portion of minor cutting edge 6 7 Mounting hole 8, 8A, 8B Groove 9 Narrow portion 10 Nick 11 End mill body 12 (12A, 12B) Insert mounting seat 14A, 14B, 14C Protrusion M Position of nick 10 that is most recessed toward seating surface 3 P Center of arc formed by arcuate cutting edge portions 5a and 6a of major cutting edge 5 and minor cutting edge 6 Q5 arcuate cutting edge of major cutting edge 5 Contact point between portion 5a and linear cutting edge portion 5b Q6 Contact point between arcuate cutting edge portion 6a of minor cutting edge 6 and linear cutting edge portion 6b S5 Most convex point of major cutting edge S6 Most convex point of minor cutting edge L5 Center Straight line connecting P and major cutting edge convexity point S5 Straight line connecting center P and minor cutting edge convexity point S6 The angle at which the straight line L5 intersects the portion extending from the center P to the end opposite to the contact point Q5 in the cross section along the rotation axis of the rotation locus of the main cutting edge 5 about the rotation axis parallel to the portion 5b. From the center P of the cross section along the rotation axis of the rotation trajectory of the minor cutting edge 6 around the rotation axis that passes through the center P of the arc-shaped cutting edge portion 6a of the blade 6 and is parallel to the linear cutting edge portion 6b to the point of contact Q6 Angle at which straight line L6 intersects with portion extending to the opposite end side O Axis of end mill main body 11 T End mill rotation direction

Claims (6)

A cutting insert detachably attached to an insert mounting seat formed at the tip of an end mill body of an indexable ball end mill that rotates around an axis,
A rake face directed in the direction of rotation of the end mill body, a seating surface facing the opposite side of the rake face and seated on the bottom surface of the insert mounting seat, and a flank extending around the rake face and the seating face. and
An arcuate cutting edge portion extending in an arcuate shape in a plan view viewed from the direction facing the rake surface and an arcuate cutting edge portion extending in contact with the arcuate cutting edge portion are provided at the intersecting ridgeline portion between the rake face and the flank face. two cutting edges each having a linear cutting edge portion are formed by alternately positioning the arcuate cutting edge portion and the linear cutting edge portion in the circumferential direction of the rake face,
One of the two cutting edges is a major cutting edge and the other is a minor cutting edge,
The arc-shaped cutting edge portion of the major cutting edge is formed to have a longer circumferential length with a radius equal to that of the arc-shaped cutting edge portion of the minor cutting edge,
The rake face of the main cutting edge is formed with a groove-like nick that reaches the main cutting edge and opens to the flank face,
At least in the main cutting edge, the arc-shaped cutting edge portion is formed in a convex curved shape that moves away from the seating surface side and then approaches the seating surface side as it separates from the linear cutting edge portion except for the nick. has a basic shape,
The nick is arranged at a position different from the most convex point of the main cutting edge where the arcuate cutting edge portion in the basic shape of the main cutting edge is most convex with respect to the seating surface ,
In the main cutting edge, in the cross section along the rotation axis of the rotation locus of the main cutting edge around the rotation axis that passes through the center of the arc-shaped cutting edge portion in plan view and is parallel to the linear cutting edge portion ,
A portion of the rotating shaft extending from the center of the arc-shaped cutting edge portion to the end portion side opposite to the contact point of the arc-shaped cutting edge portion with the linear cutting edge portion; A cutting insert characterized in that a straight line connecting the convex points intersects at an angle within the range of 43° to 47° . At least one nick of the main cutting edge is arranged on an end side opposite to the point of contact between the arcuate cutting edge portion and the linear cutting edge portion with respect to the main cutting edge most convex point. The cutting insert according to claim 1, characterized by: A groove-shaped nick that reaches the minor cutting edge and opens to the flank is formed on the rake face of the minor cutting edge,
Except for the nick, the arc-shaped cutting edge portion of the minor cutting edge is formed in a convex curved shape that moves away from the seating surface side and then approaches the seating surface side as it separates from the linear cutting edge portion of the minor cutting edge. has a basic shape,
The nick of the minor cutting edge is such that the most recessed position toward the seating surface in the opening to the flank is the most convex of the arcuate cutting edge portion in the basic shape of the minor cutting edge with respect to the seating surface. 3. The cutting insert according to claim 1, wherein the cutting insert is arranged at a position different from the most convex point of the minor cutting edge. The nick of the minor cutting edge is such that the most recessed position on the seating surface side in the opening to the flank face is located between the arcuate cutting edge portion and the linear cutting edge portion relative to the most convex point of the minor cutting edge. 4. The cutting insert according to claim 3 , characterized in that it is arranged on the side of contact with the. In the minor cutting edge, in the cross section along the rotation axis of the rotation locus of the major cutting edge around the rotation axis passing through the center of the arcuate cutting edge and parallel to the linear cutting edge in plan view ,
A portion of the rotating shaft extending from the center of the arc-shaped cutting edge portion to the end portion side of the arc-shaped cutting edge portion opposite to the contact point with the linear cutting edge portion; 5. The cutting insert according to claim 3, wherein the straight line connecting the convex points intersects at an angle within the range of 43° to 47°. The cutting insert according to any one of claims 1 to 5 is detachably attached to an insert mounting seat formed at the tip of an end mill body that rotates about an axis. indexable ball nose end mill.

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